If you have a fire, smoke alarms can cut nearly in half your risk of dying in a fire. Smoke alarms sense abnormal amounts of smoke or invisible combustion gases in the air. They can detect both smoldering and flaming fires.In new homes: The National Fire Alarm Code (NFPA 72) requires hard-wired, interconnected smoke alarms with battery back-up on every level of the home, outside each sleeping area, and inside each bedroom. Alarms must be wired together so that if one sounds, they all sound.In existing homes: If smoke alarms are not already in place, at a minimum install them on every level of the home and outside each sleeping area. If a fire occurs inside a bedroom, dangerous gases can cause heavier sleep. For the best protection, install interconnected smoke alarms in each bedroom and throughout the home. When one sounds, they all sound.To prevent nuisance alarms, vacuum cobwebs and dust from your smoke alarms monthly. Never disable a smoke alarm, even if you experience nuisance alarms while cooking or showering. Instead, use the alarm’s “hush” button. If nuisance alarms are a persistent problem, look for a different type of smoke alarm and ensure they are installed in correct areas in the home.Use the test button to test your smoke alarms at least monthly. The test feature tests all electronic functions and is safer than testing with a controlled fire (matches, lighters, cigarettes).If the manufacturer's instructions permit the use of an aerosol smoke product for testing the smoke alarm, choose one that has been examined and tested by a third-party product testing laboratory, and use it in accordance with the product instructions.If you have battery-powered smoke alarms, replace the batteries at least once a year. Some agencies recommend that you replace batteries when the time changes from standard to daylight savings each spring and then back again in the fall. "Change your clock, change your batteries." Replacing batteries this often will not hurt, but fresh batteries typically last at least a year, so more frequent replacement is not necessary unless the smoke alarm begins to chirp.If your local area does not observe daylight savings time, pick an easy-to-remember anniversary, such as your birthday or a national holiday, as the day to change the batteries each year.Replace the batteries in your carbon monoxide (CO) alarms at the same time you replace your smoke alarm batteries.Replace your smoke alarms every 10 years. This is the recommendation of the National Fire Protection Association and the U.S. Consumer Product Safety Commission. Smoke alarms become less sensitive over time.Be sure to install smoke alarms in areas where pets are and in other buildings that house animals where humans can hear them.